def UTCtoJDN(d):
    """
    This function takes a datetime described in UTC and returns the JDN
       known as the julian day number.
    """
    import wx
    import datetime

    dt = datetime.datetime.fromtimestamp(d)
    wd = wx.DateTime.Now()
    wd.Set(dt.day, dt.month-1, dt.year, dt.hour, dt.minute, dt.second, dt.microsecond/1000.0)
    return wd.GetJDN()

